1. Field of Invention
The present invention relates to a ship product, and more particularly to a submarine able to sail on water or under the water, having a water-borne displacement and a submerged displacement equal to each other.
2. Description of Related Arts
According to records, an earliest submarine appeared during American Revolution. After 200 years' development, from an early manpower submarine to a diesel-electric submarine and a nuclear power submarine, the submarine has become an important part of a modern navy. However a diving principle of the submarine has not changed. The diving principle is that a specific gravity of the submarine is changed via inhaling or blowing out seawater, in such a manner that the submarine is able to dive or surface. Therefore all of the modern submarines have double-skin structures, wherein a pressure hull inside is a cylinder having high roundness, and personnel, equipments, etc. are all in the pressure hull. A nonpressure hull outside is in a shape having low water resistance, e.g. water-drop shapes, a water box between the two hulls controls the submarine to dive or surface, and the non-pressure hull is able to resist attacks of underwater ordnances, e.g. depth bombs, to some extent. As a tactics or strategic weapon, the modern submarine has developed well, but the submarine still has some disadvantages such as a low deadweight, a low tank capacity and a complicated structure. When the submarine is sailing under water, a submerged displacement is larger than a water-borne displacement, so the water resistance is increased. With a large tank of water added, an underwater mobility of the submarine is not good. Therefore, applications of the modern submarines are limited, and usually limited to an assault weapon.